Chlamydophila pneumoniae HflX belongs to an uncharacterized family of conserved GTPases and associates with the Escherichia coli 50S large ribosomal subunit.
Predicted members of the HflX subfamily of phosphate-binding-loop guanosine triphosphatases (GTPases) are widely distributed in the bacterial kingdom but remain virtually uncharacterized. In an attempt to understand mechanisms used for regulation of growth and development in the chlamydiae, obligate intracellular and developmentally complex bacteria, we have begun investigations into chlamydial GTPases; we report here what appears to be the first analysis of a HflX family GTPase using a predicted homologue from Chlamydophila pneumoniae. In agreement with phylogenetic predictions for members of this GTPase family, purified recombinant Cp. pneumoniae HflX was specific for guanine nucleotides and exhibited a slow intrinsic GTPase activity when incubated with [gamma-(32)P]GTP. Using HflX-specific monoclonal antibodies, HflX could be detected by Western blotting and high-resolution confocal microscopy throughout the vegetative growth cycle of Cp. pneumoniae and, at early time points, appeared to partly localize to the membrane. Ectopic expression of Cp. pneumoniae HflX in Escherichia coli revealed co-sedimentation of HflX with the E. coli 50S large ribosomal subunit. The results of this work open up some intriguing possibilities for the role of GTPases belonging to this previously uncharacterized family of bacterial GTPases. Ribosome association is a feature shared by other important conserved GTPase families and more detailed investigations will be required to delineate the role of HflX in bacterial ribosome function.
Polkinghorne
Adam
A
Institute of Veterinary Pathology, University of Zurich, Winterthurerstrasse 268, Zurich 8057, Switzerland.
Ziegler
Urs
U
Institute of Anatomy and Center for Microscopy and Image Analysis, University of Zurich, Winterthurerstrasse 190, Zurich 8057, Switzerland.
González-Hernández
Yanela
Y
Institute of Organic Chemistry, ETH Hönggerberg, Zurich 8093, Switzerland.
Pospischil
Andreas
A
Institute of Veterinary Pathology, University of Zurich, Winterthurerstrasse 268, Zurich 8057, Switzerland.
Timms
Peter
P
Institute of Health and Biomedical Innovation and School of Life Sciences, Faculty of Science, Queensland University of Technology, Brisbane, Australia.
Vaughan
Lloyd
L
Institute of Veterinary Pathology, University of Zurich, Winterthurerstrasse 268, Zurich 8057, Switzerland.
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D016993:Chlamydophila pneumoniae / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D019143:Evolution, Molecular; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D008969:Molecular Sequence Data; D005810:Multigene Family; D011485:Protein Binding; D054681:Ribosome Subunits, Large, Bacterial / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment
D001426:Bacterial Proteins; D020558:GTP Phosphohydrolases